Poly cased ammo on the shelves

[DAS HUGH!]

I'm no scientist but based on the Law of Thermal Transfer (LTT), I don't see how the poly case leads to less heat.

I can see based on the LTT how a brass or steel case will absorbs some of the total heat energy generated thus meaning a cooler firearm as the portion absorbed by the case never gets transferred to the firearm.

Yeah as I said there's a logical debate being had on both sides of this issue especially. As I said I can see it both ways. The truth is likely somewhere in the middle like with many things, even with several things being true at one time. Sort of one of those deals where there's no wrong sides but both are right in many aspects.
The parts that makes me think that there must be some truth to it is...
A. I'm sure the military tested the claims. I guess all ya need is a thermometer gun, and run x amount of both ammo types thru the same guns and then zap it and get your answer.
B. Metals do conduct heat far better than plastics to begin with.
C. The casings aren't scorched or melted during or after being fired. If they started coming out melted I would think that would be easy to see pretty quick.
D. I think I recall it's part of how they got the MG version to run for so cool for so long, even suppressed. Which by what I saw was impressive I admit. (BTW, they developed this whole cartridge and all for the MG version to begin with. Then designed the LT to pair with it as a secondary objective later. So when people judge the LT as if it was made first and is a stand alone rifle I don't think that's exactly fair. It yes has a few detractions but when judged as a combined package to share lighter, stronger ammo and carry more of it, extend the reach of a units firing ability, and all that I think there's alot to be said there vs our LMG gunners being tied down to 556 like now to keep ammo types the same.) Sorry had to insert that long nugget to be fair.
E. I guess you can pick up the casing after being shot out and feel how hot it is.

But. With all that being said. I know ealier guns that HK and others tried I think had an issue of cooling off after sustained strings of fire. Not sure how they get around this issue yet.
With semi auto and bolt guns I'm sure it's likely not a big issue.
But... I can't help but wonder what happens when you do a few mag dumps in full auto then stop shooting. What happens then? Does the plastic round just sit in the hot chamber and smolder? So I'll have to look but I'm assuming they'd have to use an open bolt design to make this a non issue?
It's definitely a curious topic tho. It's been over a year since I watched it and my memory is terrible. So I'll have to check into it all again soon. Especially the Fury ones.

 

[FrommerStop]

I've only briefly read about it and watched a video or two as far as the Spear program was involved with some.
But...
It's main selling point was higher PSI being able to be made. I forget why exactly.
That.. and it's supposed to make guns in full auto run cooler. They say...
But it's part of why SIG was able to make such high pressure claims on the new rigs. The numbers many wasn't impressed by tho. But.. those who griped was comparing it to numbers out of 18+ inch barrel calibers of similar numbers. Sig did it with shorter barrels. So there's something to be said there about it.
There's debate on the cooling factor tho. Some stay the conventional ejecting brass carries heat out during extraction and away out of the gun. But the makers of the poly claim the casing don't transfer the heat to begin with tho. So yeah I'll have to read up again on it all and do a circle back Jen on the matter lol.

I have always read that the brass cases removed heat from the gun.